I am having a house built and the builder found organic soils during the excavation. They removed the soils and then filled the cavity with 1x3 stone (see picture). This is the corner where the sump crock is supposed to be and I am concerned that the digging of the hole for the sump will unsettle the stone. The builder doesn't think so. My question is should I be concerned about this or will disturbing the stone undermine the foundation. Thank you.
If the excavation has a slope of roughly 3 vertical to 1 horizontal, that's about 70 degrees with horizontal. An unloaded slope in stones, gravel or sand will not be stable at an angle of more than approximately 40 degrees with horizontal, so it is not possible to make the excavation without disturbing the soil. That angle is called the angle of internal friction and is considered a material parameters that describes the quality of the soil. The value of 40 degrees is an estimate of mine that I am guessing might be applicable to your stone fill, and it assumes a well-compressed fill of decent quality stones. And furthermore, it does not include any safety factors, so the slope of the excavation should be further reduced to about 35 degrees with horizontal.
Instead of moving the sump crock away from the foundation, you could consider installing a small retaining wall.